The average household size of an occupied unit is a measure obtained by dividing the number of people living in occupied housing units by the total number of occupied housing units. This measure is rounded to the nearest hundredth.

Excerpt from:

Social Explorer, U.S. Census Bureau; 2010 Census of Population and Housing, Summary File 1: Technical Documentation, Issued June 2011.

A housing unit is owner-occupied if the owner or co-owner lives in the unit even if it is mortgaged or not fully paid for. The owner or co-owner must live in the unit and usually is Person 1 on the questionnaire. The unit is Owned by you or someone in this household with a mortgage or loan if it is being purchased with a mortgage or some other debt arrangement, such as a deed of trust, trust deed, contract to purchase, land contract, or purchase agreement. The unit is also considered owned with a mortgage if it is built on leased land and there is a mortgage on the unit.

A housing unit is Owned by you or someone in this household free and clear (without a mortgage or loan) if there is no mortgage or other similar debt on the house, apartment, or mobile home, including units built on leased land if the unit is owned outright without a mortgage. Although most tables show total owner-occupied counts, selected tables separately identify the two owner categories.

All occupied housing units which are not owner-occupied, whether they are rented or occupied without payment of rent, are classified as renter-occupied. Rented includes units in continuing care, sometimes called life care arrangements. These arrangements usually involve a contract between one or more individuals and a service provider guaranteeing the individual shelter, usually an apartment, and services, such as meals or transportation to shopping or recreation. The no rent paid category includes units provided free by friends or relatives or in exchange for services, such as a resident manager, caretaker, minister, or tenant farmer. Housing units on military bases are also classified in the No rent paid category.

Data on tenure have been collected since 1890. In 1990, the response categories were expanded to allow the respondent to report whether the unit was owned with a mortgage or loan, or free and clear (without a mortgage). The distinction between units owned with a mortgage and units owned free and clear was added in 1990 to improve the count of owner-occupied units. Research after the 1980 Census indicated some respondents did not consider their units owned if they had a mortgage. In Census 2000, we continued with the same tenure categories used in the 1990 Census. In 2010, the instruction Include home equity loans was added following the response category Owned by you or someone in this household with a mortgage or loan? Additional changes included revising the wording of two response categories from Rented for cash rent? to Rented? and Occupied without payment of cash rent? to Occupied without payment of rent?